The present invention concerns a radio communication device and the corresponding process for establishing a communication.
The invention is applied more particularly although not exclusively to establishing a communication between the crew members of an aircraft and the ground staff of an airport where the aircraft is touching down.
It is known that, when an aircraft arrives on a site, it is necessary for the members of the crew to restore a link to the ground staff. The first communication to be established is that which provides a link between the pilot and the runway staff responsible for directing the aircraft to its parking position. The radio frequencies which are usually employed for communication with the control tower generally being close to saturation, it is not possible to envisage using those frequencies for communication with the ground staff.
In the absence of suitable means for a radio communication, the communication between the pilot and the runway staff is therefore implemented visually by gestures. Irrespective of the difficulties that such a communication can involve under certain meteorological conditions when visibility is poor, it is necessary for the runway staff to be in the field of vision of the pilot, which in itself is a very major operational constraint.
When the aircraft has reached its parking position, it is known to establish a communication between the runway staff and the aircraft crew by connecting an external communication circuit to the internal communication circuit of the aircraft. That link is made by means of a wire and also constitutes a serious constraint which affects the freedom of movement of the ground staff.
In order to remedy those disadvantages, as disclosed in particular in document WO 94/28684, it has been envisaged that communications can be established between the crew members of an aircraft and the ground staff by using the existing radio communication networks which make it possible in particular to establish a communication between itinerant subscribers which are the crew members of the aircraft and resident subscribers which are the members of the ground staff of an airport, in particular the runway staff. However, by virtue of the itinerant subscribers being related to a site of origin, the cost of such communications is high so that this communication system is not the optimum one.
Taking into account the apparent mobility of the itinerant subscribers and the apparent immobility of the resident subscribers, consideration has also been given to locally creating a radio communication system comprising a base station carried by a resident subscriber and considering the aircraft as mobile stations provisionally associated with the base station in accordance with the link which is usually implemented in a conventional radio communication system between a mobile station and a base station. However it was found that a structure of this type was not suited to setting up a communication of a number of runway staff members with the same aircraft, which however it is desirable to be able to implement.
In accordance with the invention there is proposed a radio communication system between at least one itinerant subscriber installed in a vehicle irrespective of the type of such vehicle (aircraft but also train, boat or ship, truck . . . ) and at least one resident subscriber installed on a site, the radio communication system comprising a base station installed on the vehicle and directly associated to at least one mobile station possessed by a resident subscriber on the site.
Thus, by a reversal of the usual structure of the system, a central function, in relation to the communications envisaged, is given to the aircraft or more generally to the vehicle carrying the base station, which makes it possible in particular by a procedure for unique identification of the base station to produce a relationship between a plurality of itinerant subscribers with the resident subscribers when the aircraft arrives on a site.
In accordance with another aspect of the invention it concerns a process for establishing a communication between at least one itinerant subscriber in a vehicle and at least one resident subscriber on a site, by means of a radio communication system comprising a base station installed on the vehicle and at least one mobile station possessed by a resident subscriber, said process comprising the steps of detecting in the base station upon the arrival of the vehicle on a site available time windows and emitting in said time windows a signal representative of an identity of the vehicle in order to make itself directly known to the mobile stations present on the site. Thus, by ensuring that identification of the vehicle is effected in an available time window, it is possible for all the resident subscribers listening in within a suitable range to detect the arrival of the vehicle, in which respect the different vehicles on the site can thus be detected and identified.
To carry the process into effect, the identity of the vehicle giving rise to the emission of a signal can be a permanent identity (registration or record number of the vehicle) or a provisional identity which is representative of the transport operation (flight number or manifest number . . . ) or an association of those types of identity.
In accordance with a further advantageous aspect of the invention the process comprises the step of exchanging the directory data between the base station and at least one mobile station. The term directory data is used to denote not only the name of the subscribers but also other items of useful information for the establishment of communications such as link organisations or the functions of the subscribers. The resident subscribers and the itinerant subscribers are thus respectively informed of the local call numbers and identifications of the persons communicating therewith, in such a way that communications can be easily established between the itinerant subscribers and the resident subscribers.